IPv6

From version 207 and 21x, systemd only applies settings from /etc/sysctl.d/*.conf and /usr/lib/sysctl.d/*.conf.

/etc/sysctl.conf
/etc/sysctl.d

https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1

sysctl -a | grep accept_ra
sysctl -a | grep autoconf